Packet conversion apparatus and system

ABSTRACT

A packet conversion apparatus includes a detector for detecting heads of transmission packet signals, a packetizer responsive to the detecting means for packetizing the transmission packet signals by sequentially arranging them into one or more recording packets to specify positions of the prescribed number of transmission packets for one or more recording packets, a source for supplying reserved data, and a combiner for inserting the reserved data into a space of the recording packets where no transmission packet signals are present.

FIELD OF THE INVENTION

The present invention relates to a packet conversion apparatus and apacket conversion system, and more particularly to a packet conversionapparatus and a system suited for use in a recording reproducingapparatus for recording transmission packet signals by converting thetransmission packet format into a prescribed recording packet format.

BACKGROUND OF THE INVENTION

In a data communication field, a packet communication system whichtransmits information by breaking the information into blocks and addingadditional information for identifying the data has been so far adopted.For digital visual imaging communication, it is also attempted totransmit compressed image data by packetizing.

FIGS. 1 and 2 are diagrams showing exemplified formats of transmissionpackets.

FIG. 1 shows an example of the transmission packet for use intransmission of data packets m, m+1, m+2, . . . by sequentiallyarranging them, but without synchronizing them with a prescribed syncsignal. Each packet comprises a header (H) for use in identifying datain the packet, transmission data and an error correction parity (P) foruse in correcting errors in the packet.

On the other hand, FIG. 2 shows an example of a transmission packet foruse in the transmission of M packets synchronous with, for instance, areference cycle of the frames, etc. of video signals. In FIG. 2, oneframe is comprised of k packets of data corresponding to respectivecolumns, and each datum of the k packets is comprised of a header H,transmission data, and an error correction parity P. Further, the headerH1 of the first packet (M=1) also serves as the header for use inidentifying an entire data of the k packets in the n-th frame. Further,the size of the header may vary according to its column position M.

By the way, the size of these packets and the recording unit of arecording apparatus may differ from each other. In this case, packetdata are recorded by converting them into a recording format. Forinstance, the Japanese Patent Application Tokkai-Hei 4-86181 titled asRecording Reproducing Apparatus discloses that transmitted packets areconverted into recording packets with a recording format for VTRs. Therecording packet disclosed in the Application Tokkai-Hei 4-86181 iscomprised of screen positional information MBA (Macro Block Address) anda sync block record start positional information MBP (Macro BlockPointer), both added into the transmission data in the unit of a syncblock.

FIGS. 3 and 4 are block diagrams showing the construction of theJapanese Patent Application titled as the Recording Reproducingapparatus, while FIGS. 5(a), 5(b) and 5(c) are diagrams for explainingthe recording packet of the present invention.

FIG. 3 is a block diagram showing another conventional packet conversionapparatus associated with other conventional recording packets, as shownin FIGS. 5(a) and 5(b)

Transmission packet signals are supplied to a receiving circuit 1, andthen are transferred to a packetizer 3 via a buffer 2. The buffer 2 isused for adjusting the timings of data processed in later stages. Thepacketizer 3 converts the transmission packet signal into another packetformat signal suited for a recording system, e.g., VTRs.

The recording format of a VTR is basically configured by unit ofrecording tracks. FIGS. 5(a), 5(b) and 5(c) show three types ofrecording formats each configured for one record track, wherein onetrack is comprised of M' packets. Each packet constitutes a sync block(sync unit).

FIG. 5(a) shows an example of the recording track wherein transmissionpacket signals are sequentially arranged in the transmission order bythe packetizer 3. That is, in this case, header and transmission datacontained in the transmission packets are arranged in the recordingpacket in their original order. The recording packets configured in thepacketizer 3 are applied to an error correction encoder 4. The errorcorrection encoder 4 adds an error correction parity P into each of therecording packets and provides the resulted recording packets to acombiner 5. Further, an ID generator 6 generates ID data including tracknumber ID data, sync number ID data and other important ID data, andsupplies the ID data to the combiner 5. The combiner 5 combines a syncsignal SYNC at the head of each recording packet, and then arranges theID data, information data and the error correction parity P in therecording packet at a prescribed order.

Further, the recording packet shown in FIG. 5(b) represents that theheaders and the information data in the transmission packets are eachdivided into pieces in the recording packets, respectively. In thiscase, the information data contained in transmission packets areprovides from the buffer 2 to the-packetizer 3, while headers areprovided from the buffer 2 to a header packetizer 8. The headerpacketizer 8 packetizes the headers and provided the resulted packets toanother combiner 7. In this case, the headers are not yet contained inthe output of the combiner 5. The combiner 7 arranges the informationdata and the headers individually and then provides the resultedrecording packets.

In the recording packet, as shown in FIG. 5(a), wherein the transmissionpacket data are sequentially allocated, that is, all the data containingheaders and parities of the transmission packets are continuouslyallocated, it is not possible to suppress the propagation of errors. Forinstance, if any error had occurred in the data within the packet, theerror position will be found by an error flag. However, unless the syncsignal for the transmission packet can be surely detected, it is notpossible to restore the original format of the transmission packetsduring it decoding operation. That is, the sync block in which an errorhad occurred falls in same state as the packet that lacks some data.Further, it becomes impossible to carry out a correction or aninterpolation, etc. on the sync block. However when the detection of thesync signal is secured, it is possible to detect the heads of the packetfrom data in which no errors occur.

Further, when data and a header are each divided into pieces, as shownin FIG. 5(b), the boundaries of the data will become indefinite. Then,in the case where variable-length codes, etc. are adopted, the headerposition of a data portion having no errors cannot be detected and apropagation of errors becomes large as in the case shown in FIG. 5(a).

So, in the conventional packet conversion apparatus as disclosed in theabove-mentioned Japanese Application with the title of RecordingReproducing Apparatus, a method has been also disclosed for suppressingthe propagation of errors even when variable length coded data are inputas transmission data. Further, in the present invention picture data aredivided into luminance blocks and color difference blocks each having aprescribed volume, respectively. Additionally, a macro block isconstructed using a plurality of sub-blocks for use as a unit ofpredictive coding.

In FIG. 4. transmission packet signals supplied to the receiving circuit1 are then transferred to an MB (Macro Block) head detector 11 and aheader packetizer 12 via the buffer 2. The MB head detector 11 transfersthe transmission data to a data packetizer 13. The MB head detector 11also detects the head of a macro block from the transmission data andthen provides the macro block information to an MBA (Macro BlockAddress) generator 14. The data packetizer 13 packetizes informationdata and then provides the packetized data to an MBP (Macro BlockPointer) generator 15 and a combiner 16.

The MBA generator 14 generates an MBA (Macro Block Address) showing anaddress on the screen to which the macro block corresponds and thenprovides it to the combiner 16. Further, the MBP generator 15 generatesan MBP (Macro Block Pointer) which is the head positional information ina sync block of the macro block and then provides it to the combiner 16.The combiner 16 combines encoded data corresponding to respective screenareas following the macro block address and the macro block pointer andthen provides it to the error correction encoder 4. The error correctionparity P from the error correction encoder 4 and ID data from the IDgenerator 6 are arranged in another combiner 17. Thus, as shown in FIG.5(c), encoded data corresponding to respective screen areas are addedwith an error correction parity and arranged after the sync signal(SYNC), the ID data, the MBA (Macro Block Address) and the MBP (MacroBlock Pointer) in units of one sync block. Further, the headerpacketizer 12 packetizes headers and sends it to still another combiner18 for multiplexing with the output of the combiner 17. Recording trackdata are thus formed.

As described above, in this case, the propagation of errors issuppressed by extracting the screen positional information contained intransmission packets and recording two kinds of information, i.e., thescreen positional information MBA indicating the correspondence betweenthe data and the screen, and the positional information MBP showing datapositions in recording packets.

However, the apparatus shown in FIG. 4 generates the MBA and the MBP byextracting additional information contained in transmission packetswhere there was such a problem that the circuit scale increases greatly.

As described above, in a conventional packet conversion apparatus, inorder to suppress the propagation of errors, the positional information,MBP, and the screen positional information MBA are generated byextracting additional information contained in the transmission packetswhen converting transmission packets into recording packets and there issuch a in problem that the circuit scale increases greatly.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a packetconversion apparatus Which is capable of suppressing the propagation oferrors and reducing the circuit scale.

In order to achieve the above object, a packet conversion apparatusaccording to one aspect of the present invention includes a detector fordetecting the headers of transmission packet signals, a packetizerresponsive to the detecting means for packetizing the transmissionpacket signals by sequentially arranging them into one or more recordingpackets to specify positions of the prescribed number of transmissionpackets for one or more recording packets, a source for supplyingreserved data, and a combiner for inserting the reserved data into aspace of the recording packets where no transmission packet signals arepresent.

In the present invention, the head detection means detects the head oftransmission packets. The packetizing means packetizes the prescribednumber of transmission packets by sequentially arranging them over oneor more recording packets based on the detection result. As a result,the head of the prescribed number of transmission packets appears at,for instance, the head of one or more recording packets. The reserveddata source supplies the reserved data or the dummy data into a portionof the recording packets, where no transmission packet has beenarranged, and outputs the recording packets. Further, when arrangingtransmission packets continuously in recording packets in a prescribedlength, the head position of transmission packets on the recordingpackets is detected and the positional information indicating the headof the transmission packet signal on the recording packet is generatedby the position detecting means. By inserting the positional informationinto a prescribed position on the recording packets by the insertingmeans, it becomes possible to find the correspondence between recordingpackets and transmission packets.

Additional objects and advantages of the present invention will beapparent to persons skilled in the art from a study of the followingdescription and the accompanying drawings, which are hereby incorporatedin and constitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 is a diagram for explaining one example of transmission packets:

FIG. 2 is a diagram for explaining another example of transmissionpackets;

FIG. 3 is a block diagram showing a conventional packet conversionapparatus;

FIG. 4 is a block diagram showing another conventional packet conversionapparatus;

FIGS. 5(a), 5(b) and 5(c) are diagrams for explaining recording packetsachieved by the conventional packet conversion apparatuses;

FIG. 6 is a block diagram showing a first embodiment of a packetconversion apparatus according to the present invention;

FIG. 7 is a diagram for explaining an example of recording packetsachieved by the embodiment of FIG. 6;

FIG. 8 is a diagram for explaining another example of recording packetsachieved by the embodiment of FIG. 6;

FIG. 9 is a diagram for explaining still another example of recordingpackets achieved by the embodiment shown in FIG. 6;

FIG. 10 is a block diagram showing a second embodiment of a packetconversion apparatus according to the present invention;

FIG. 11 is a block diagram showing an exemplified construction of thememory of FIG. 10;

FIG. 12 is a block diagram showing a third embodiment of a packetconversion apparatus according to the present invention;

FIG. 13 is a diagram for explaining an example of recording packetsachieved by the embodiment of FIG. 12; and

FIGS. 14 through 24 are diagrams for explaining modifications of thepacket conversion according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail with reference to theFIGS. 6 through 24.

FIG. 6 is a block diagram showing a first embodiment of the packetconversion apparatus according to the present invention.

Transmission packet signals are input to a receiving circuit 1. Thereceiving circuit 1 demodulates the transmission packet signals andtransfers them to a buffer 2. The buffer 2 temporarily holds thedemodulated transmission packet signals, and then provides them to apacketizer 21 and a packet head detector 22. The packet head detector 22detects the head of the transmission packet signals in search of headersof the transmission packets and then provides the resulted detectionsignal to the packetizer 21.

In this embodiment, the packetizer 21 packetizes n' pieces oftransmission packet signals into N' (N'+n') pieces of recording packets,based on the detection signal directing the head of transmissionpackets. For instance, if the length of transmission packets and thelength of recording packets are such that [the length of recordingpackets×2]>[the length of transmission packets]>[the length of recordingpackets], the packetizer 21 packetizes the transmission packet signalsassuming that, for instance, N'=2 and n'=1. The packetizer 21 arrangestransmission packet signals in series starting from its head.Accordingly, under the conditions, the transmission packet signals arearranged for the whole of the first recording packet and only the headof the second effective recording field of two recording packets and aportion with no transmission packets arranged will be produced in thetrailing end of the second effective recording field.

The packetized recording format signals output from the packetizer 21 isapplied to a combiner 23. An output of a reserved data source 24 is alsoapplied to the combiner 23. The reserved data source 24 suppliesreserved data or dummy data of, for instance, continued "1", etc. Thecombiner 23 selects the outputs of the packetizer 21 and the output ofthe reserved data source 24 by switching them at prescribed regularintervals and inserting the reserved data or the dummy data into aportion with no transmission packet arranged in the trailing end of thesecond recording packet, outputs the recording packet to the errorcorrection encoder 4.

The error correction encoder 4 outputs each recording packet data byadding the error correction parity to another combiner 25. The IDgenerator 6 generates the sync signal (SYNC) and ID data of eachrecording packet and applies them to the combiner 25. The combiner 25add the sync signal (SYNC) and ID data to the head of each recordingpacket and outputs as a recording packet.

Next, the operation of the embodiment in the construction as describedabove will be explained with reference to the explanatory diagram shownin FIG. 7.

The receiving circuit 1 demodulates the transmission packet signals andtransfers them to the packetizer 21 and the packet head detector 22 viathe buffer 2. The header of the transmission packet contains the headposition data. Further, the header may contain the information on screenposition of data, etc. Therefore, if in this case the transmissionpacket signals have been continuously reproduced, it is possible todetect positions on the screen and also positions in the transmissionpackets by extracting the headers of the transmission packets. However,as the heads of the transmission packets are unknown, if an error isgenerated as described above, it is not necessarily possible to usetransmission packets in demodulation even when the lengths oftransmission packets are constant.

On the contrary, in this embodiment it is made possible to identify thetransmission packet signals by identifying recording packets through thefixture of the correspondence of transmission packets to recordingpackets. That is, the packet head detector 22 detects the head of thetransmission packet signal in search of the header contained in thetransmission packet signal read from the buffer 2 and applies thedetection signal to the packetizer 21. If [recording packet length×2]>[transmission packet lenght]>[recording packet lenght], thepacketizer 21 packetizes one transmission packet for two recordingpackets as shown in FIG. 7. That is, the front parts of the transmissionpackets PT1, PT2, . . . are sequentially arranged to the first recordingpackets PR11, PR21, . . . starting from the head, and the remainingparts of the transmission packets PT1, PT2, . . . are sequentiallyarranged to the recording packets PR12, PR22, . . . Since [recordingpacket length×2]>[transmission packet lenght]>[recording packet lenght],in the trailing ends (shown in the shaded regions) of the secondrecording packets PR12, PR22, . . . , portions with no transmissionpackets arranged will be produced. As a result of this packetizing, then' pieces of the transmission packets are always arranged at prescribedpositions of the N' pieces of the recording packets and thecorrespondence between the recording packets and the transmissionpackets will become clear.

The output of the packetizer 21 is applied to the combiner 23 and thusthe reserved data or the dummy data from the reserved data source 24 areinserted in the recording packets at the timing of the shaded regions,as shown in FIG. 7. The error correction encoder 4 applies the output ofthe combiner 23 with the error correction parity P added to the combiner25. The output of the ID generator 6 is also applied to the combiner 25.The combiner 25 arranges the sync signal (SYNC) and ID data from the IDgenerator 6 at the head of the recording packets as shown in FIG. 7 andoutputs the recording packets.

As described above, the packetizer 21 packetizes one transmission packetsignal over two recording packets in this embodiment. Accordingly, thehead of a transmission packet signal will be arranged to every otherrecording packet in this case. Therefore, even if an error is generated,it is possible to identify transmission packet signals after restoredfrom the error from ID of recording packets and thus, a propagation oferrors can be suppressed.

Further, in the above embodiment, values of N' and n' may be determinedaccording to the relationship between the transmission packet length andthe recording packet length. For instance, if the unused portions asshown in the shaded regions increase when it is set as shown in theexample in FIG. 7, two transmission packets PT1 and APT2 may bepacketized over three recording packets PR1, PR2 and PR3.

Further, the embodiment described above is also applicable to cope withwhen a transmission packet length varies. FIG. 9 shows examples oftransmission packets transmitted in two different lengths. In theexamples shown in FIG. 9, the packetizer 21 executes a mode forpacketizing one transmission packet signal for two recording packets anda mode for packetizing one transmission packet signal for threerecording packets by switching them.

FIG. 10 is a block diagram showing a second embodiment of the presentinvention. In FIG. 10, the same reference numerals used in FIG. 6 willbe used to designate like or equivalent elements and the explanationwill be omitted.

In this embodiment, a memory is used for arranging transmission packetsignals. That is, transmission packet signals from the receiving circuit1 are applied to the packet head detector 22, and also to a memory 31.The memory 31 has a capacity for storing N' pieces of recording packetsand holds the reserved data or the dummy data before transmissionpackets are input. A memory read controller 33 reads the n' pieces ofthe transmission packets stored in the memory 31, based on a detectionsignal from the packet head detector 22. The memory read controller 33first reads the n' pieces of the transmission packets stored in thememory 31, and then reads the reserved data or the dummy data andprovides them to the error correction encoder 4.

FIG. 11 is a block diagram showing a definite construction of the memory31 in FIG. 10.

The memory 31 comprises three memories 31A, 31B and 31C which arerecordable the N' pieces of the recording packets.

The transmission packets are selectively provided from the receivingcircuit 1 to the three memories 31A, 31B and 31C via a switch SW1.Further, the outputs of the memories 31A, 31B and 31C are output via aswitch SW2. The switches SW1 and SW2 are controlled by the memory writecontroller 32 and the memory read controller 33, respectively.

Next, the operation of the embodiment in the construction as describedabove will be explained with reference to FIG. 11.

Transmission packet signals are supplied to the receiving circuit 1 andthen are transferred to the packet head detector 22 and the memory 31.Before writing the transmission packets into the memory 31, the reserveddata or the dummy data are written into the memory 31A. When a detectionsignal indicating the head of transmission packet is provided from thepacket head detector 22, the memory write controller 32 makes the switchSW1 select terminal b and thus the n' pieces of the transmission packetsare sequentially stored in the memory 31B. In this case, the memory readcontroller 33 causes the switch SW2 to select terminal c and thus thedata is stored into the memory 31C. As described later, the n' pieces ofthe transmission packets are already stored in the memory 31C.

When the n' pieces of transmission packet have been read from the memory31C, the memory read controller 33 causes the switch SW2 to select aterminal a so as to read out the reserved data or the dummy data storedin the memory 31A. Thus, the same recording packets as the output of thecombiner 23 shown in FIG. 6 are obtained.

At the next timing, before writing the transmission packet signals intothe memory 31, the reserved data or the dummy data are written into thememory 31C. Then, the memory write controller 32 cause the switch SW1 toselect the terminal a to start the writing of the n' pieces of thetransmission packets into the memory 31A, based on the detection signalfrom the packet head detector 22. On the other hand, the memory readcontroller 33 makes the switch SW2 to select the terminal b so as toread out the n' pieces of the transmission packets previously stored inthe memory 31B. When completing the readout operation, the memory readcontroller 33 makes the switch SW2 to select the terminal c so as toread out the reserved data or the dummy data stored in the memory 31C.

Thereafter, repeating the same operation and shifting the writingoperation and the reading operation of the transmission packets amongthe memories 31A, 31B and 31C, a plurality of recording packets with thesame format, as shown in FIG. 6, are obtained.

FIG. 12 is a block diagram showing a third embodiment of the presentinvention. In FIG. 12, the reference numerals used in FIG. 6 will beused to designate like or equivalent elements and the explanation willbe omitted.

In this embodiment, the positional information showing the head of atransmission packet signal is recorded in respective recording packetsfor making it possible to suppress a propagation of errors even when thetransmission packet signals are arranged in series.

Transmission packet signals read from the buffer 2 are applied to apacketizer 41. The packetizer 41 packetizes the transmission packetsignals by continuously arranging them in their transmission order andthen provides the resulted packets to a combiner 44 and a packet headdetector 42. The packet head detector 42 detects positional informationin recording packets, which indicates where the head of transmissionpacket signal is positioned and then provides the detected informationto a position detector 43. The position detector 43 generates apositional information indicating the head position of the transmissionpacket signals in search of a distance from the head of the recordingpacket according to the detection information and then provides thedetected positional information to another combiner 44. The combiner 44locates the positional information from the position detector 43 on thehead of the recording packet achieved by the packetizer 41 and thenprovides the resulted recording packets to the error correction encoder4.

Next, the operation of the above embodiment as constructed as shown inFIG. 12 will be explained with reference to FIG. 13. FIG. 13 is anexplanatory diagram for explaining the recording packets achieved inthis embodiment.

The transmission packet signals read from the buffer 2 are sequentiallyarranged by the packetizer 41, starting from the head of the recordingpacket. If the length of the transmission packet is longer than thelength of the recording packet but shorter than the length of tworecording packets, the transmission packet signal is arranged over tworecording packets up to the middle of the second recording packet, asshown in FIG. 13. The packet head detector 42 detects the heads of thetransmission packet signals in the recording packets as marked bysymbols (v) in FIG. 13. Then the resulted detection information isapplied to the position detector 43. The position detector 43 generatespositional data SO, S1, S2, S3, SP, S4, . . . indicating the heads ofthe transmission packet signals by the respective distances from thehead of the recording packet. As shown in FIG. 13, the combiner 44 addsthe positional data on fronts of the recording tracks achieved by thepacketizer 41. All other operations are the same as the above-mentionedembodiment of FIG. 6.

The positional information S0 and S7 added to the fronts of the firstand tenth recording packets, as shown in FIG. 13, indicate that theheads of the corresponding transmission packet signals also define theheads of the recording packets. Further, the positional information Spindicates that its associated recording packet signal does not includeany head of the transmission packet signal.

As described above, in this embodiment, as the positional information ofthe head of the transmission packet signal is added to every recordingpacket, it is easy to find the correspondence between recording packetsand transmission packets. Therefore, for instance, even when a recordingpacket drops out due to errors, it becomes easy to identify transmissionpacket signals and also to troubleshoot the VTR.

The present invention is not limited to the embodiments as describedabove, but a variety of modifications will be devised. Here, some of themodifications will be described in reference to the drawings FIGS. 14through 24.

FIG. 14 shows a first modification of the packet conversion systemaccording to the present invention. In this-first modification it isassumed that the transmission packet has the volume of 113 bytes. Thenthe first one byte on the head of the transmission packet is assigned async signal with a fixed pattern for use in the transmission. As shownin FIG. 14, the volume of respective recording packet is set to 90 byteslength. On the head of each of the recording packets 2 fields, i.e., afield of recording/reproduction sync signal with 2 bytes volume and afield of ID signal with 5 bytes volume are located. The first 3 bytes ofthe ID signal are associated with the recording packet, while theremaining 2 bytes of the ID signal are associated with the transmissionpacket. In the 90 bytes length recording packet, 75 bytes constitute aneffective recording field, and the trailing end 8 bytes are provided fora parity filed. As the transmission sync signal is of the fixed pattern,and thus the sync signal is fine to introduce in the reproducingoperation, the 112 bytes data volume of the transmission signal of thetransmission packet but without the sync signal is recorded in therecording packet.

A part of the transmission signal exceeding the volume of the effectiverecording field of one recording packet is recorded on the effectiverecording field of the next recording packet. That is, the trailing end37 (=112-75) bytes of data of the first transmission packet is notrecorded on the first recording packet, but recorded on the leading endof the second recording packet. Then although the leading end 37 bytesof data of the second transmission signal is recorded on the trailingend of the second recording packet, a 1 byte volume of reserved datafield, e.g., a dummy data field is allocated between the first andsecond transmission signals. The remaining part of the secondtransmission signal, i.e., the trailing end 75 (=112-37) bytes datavolume of the second transmission signal is recorded on the thirdrecording packet.

In the first modification as described above, the transmission signalsof the 2 transmission packets are recorded over 3 recording packets,while introducing the reserved data field or the dummy data field foruse in identifying the boundary of the succeeding two transmissionsignals

FIG. 15 shows a second modification of the packet conversion systemaccording to the present invention. In this second modification,although the packet conversion system is principally the same as that ofthe first modification. As seen from the comparison of FIGS. 14 and 15,the reserved data field is allocated on the tail end of the effectiverecording field of the third recording packet, which is different fromthe first modification.

FIG. 16 shows a third modification of the packet conversion systemaccording to the present invention. As the transmission sync signalassigned on the head of the transmission packet is of a fixed pattern,shown in FIG. 16, and thus the sync signal is introduced in thereproducing operation, the 112 bytes data volume of the transmissionsignal of the transmission packet but without the sync signal isrecorded in the recording packet. The volume of respective effectiverecording field of the recording packet is set to the 90 bytes length.On the head of each of the recording packets 2 fields, i.e., a field ofrecording/reproduction sync signal with 2 bytes and a field of ID signalwith 4 bytes are located. The first 3 bytes of the ID signal areassociated with the recording packet, while remaining 1 byte of the IDsignal is associated with the transmission packet. In the 90 byteslength recording packet, 75 bytes constitute an effective recordingfield, and the trailing end 8 bytes are provided for a parity field.Further 1 byte volume of another parity data is allocated in front ofthe 8 bytes volume of the parity field. In similar to the firstmodification, transmission signals on two transmission packets arerecorded on three recording packets. Then a 1 byte volume of reserveddata field, e.g.., a dummy data field is allocated between the first andsecond transmission signals.

FIG. 17 shows a fourth modification of the packet conversion systemaccording to the present invention. In this modification the conversionsystem same as the above three modifications is also adapted. As shownin FIG. 7, the 76 bytes data volume of each recording packet is assignedto the effective recording field, while 2 bytes data volume ofrecording/reproduction synch signal and 4 bytes data volume of ID signalare allocated on the head portion of the recording packet in the order.The first 3 bytes of the ID signal are associated with the recordingpacket, while remaining 1 byte of the ID signal is associated with thetransmission packet.

The 36 bytes data on the trailing end of the transmission packet, whichis the excess of the volume of the effective recording field of thefirst recording packet, is recorded on the effective recording field ofthe next recording packet. Further a 2 bytes data volume of additionalparity is positioned in the reserved data field or the dummy data fieldon the trail end of each transmission packet signal for use in detectingand correcting errors in each of the transmission packet signals. Thenthe signals in the second transmission packet is recorded over thetrailing end 8 bytes volume of the second recording packet and theleading end 74 bytes volume of the third recording packet. Thus a 2bytes data volume of additional parity is positioned in the reserveddata field or the dummy data field assigned to the second transmissionpacket signal.

FIG. 18 shows a fifth modification of the packet conversion systemaccording to the present invention. In this modification the reserveddata field or the dummy data field used as an additional ID signal fieldfor identifying transmission packets.

FIG. 19 shows a sixth modification of the packet conversion systemaccording to the present invention. In this modification the 112 bytesdata of each transmission packet signal are successively recorded over aplurality of recording packets. Then a 1 byte volume of reserved datafield or dummy data filed is assigned on the head portion of the firsttransmission packet signal. Further, the reserved data field or thedummy data filed is used for allocating thereon an additional ID signal.

FIG. 20 shows a seventh modification of the packet conversion systemaccording to the present invention. In this modification thetransmission sync signal in each transmission packet is recorded on therecording packet in different from the above-described modificationswhere the transmission sync signals are not recorded on the recordingpackets. That is, the entire of the 113 bytes data volume of thetransmission packet signal is recorded on the recorded packet.

The volume of respective recording packet is set to the 90 bytes length.On the head of each of the recording packets 2 fields, i.e., a field ofrecording/reproduction sync signal with 2 bytes and a field of ID signalwith 4 bytes are located. The first 3 bytes of the ID signal areassociated with the recording packet, while the remaining 1 byte of theID signal is associated with the transmission packet. The 37 bytes dataon the trailing end of the transmission packet, which is the excess ofthe 76 bytes volume of the effective recording field of the firstrecording packet, is recorded on the effective recording field of thenext recording packet. Then the second transmission packet signal isrecorded over the trailing end 39 bytes volume of the second recordingpacket and the leading end 74 bytes volume of the third recordingpacket. Thus a 2 bytes data volume of reserved data field or dummy datafield is assigned to the trail end of the second transmission packetsignal.

FIG. 21 shows an eighth modification of the packet conversion systemaccording to the present invention. In this modification, the entire 113bytes volume of the transmission packet signal is recorded over aplurality of recording packets similar to the embodiment of FIG. 19.Further, 2 bytes volume of reserved data field or dummy data field isassigned on the recording packet, but divided one by one in a mannerthat each byte of the reserved data field or the dummy data field ispositioned on the trail end of each transmission packet signal. Then thereserved data field or the dummy data field is used as a parity signalfor its corresponding transmission packet signal.

FIG. 22 shows a ninth modification of the packet conversion systemaccording to the present invention. In this modification everytransmission packet signal is recorded over two recording packets, asshown in FIG. 22. Further, in this modification the transmission syncsignal in each transmission packet is recorded on the recording packetsimilar to the above-described seventh and eighth embodiments. Thus, the113 bytes data volume of the transmission packet signal is recorded onthe recorded packet similar to the above two embodiments.

The volume of respective recording packet is set to be 90 bytes length.On the head of each of the recording packets 2 fields, i.e., a field ofrecording/reproduction sync signal with 2 bytes and a field of ID signalwith 5 bytes are located. The first 3 bytes of the ID signal areassociated with the recording packet, while the remaining 2 bytes of theID signal are associated with the transmission packet. The volume ofrespective effective recording field; of the recording packet is set to75 bytes. The leading end 74 bytes of the first transmission packetsignal are recorded on the effective recording field of the firstrecording packet, while the remaining 74 bytes of the first transmissionpacket signal are recorded on the head portion of the effectiverecording field of the second recording packet. Then the remaining 36bytes field of the effective recording field of the second recordingpacket is assigned for reserved data field or dummy data field.

In the first through ninth modifications, as shown in FIGS. 14 through22, the volumes of the transmission packet and the recording packet areset to 113 bytes in length and 90 bytes in length, respectively.However, the present invention can be also carried out by altering thevolume of either or both of the transmission packet and the recordingpacket, as shown in the following two additional embodiments withoutbeing limited to the above embodiments.

FIG. 23 shows a tenth modification of the packet conversion systemaccording to the present invention. In this modification, the volume ofthe transmission packet is set to 188 bytes in length, similar to theMPEG transport packet. While the volume of the recording packet is setto 90 bytes in length as in the above embodiments. Then the first byteon the head of the transmission packet is assigned a sync signal with afixed pattern for use in the transmission.

In this modification, the 187 bytes data volume of transmission signalof the transmission packet but without the head portion 1 byte volumesync signal is recorded in the recording packet, similar to the fourthembodiment as shown in FIG. 17. Further, reserved data field or dummydata field is assigned a portion next to the trail end of each of thetransmission packet signals. Then the reserved data field or the dummydata field is used as an additional parity signal.

As shown in FIG. 23, the first 76 bytes data of the first transmissionpacket signal is recorded on the first recording packet. The next 76bytes data of the first transmission packet signal is recorded on thesecond recording packet. Then the remaining 35 bytes data of the firsttransmission packet signal is recorded on the leading end of theeffective recording field of the third recording packet. Next, the first38 bytes data of the second transmission packet signal is recorded onthe trailing end of the effective recording field of the third recordingpacket, but spaced from the last 35 bytes data of the first transmissionpacket signal by the 3 bytes volume reserved data field or the dummydata field. The next 76 bytes data of the second transmission packetsignal is recorded on the fourth recording packet. Then the remaining 73bytes data of the second transmission packet signal is recorded on theleading end of the effective recording field of the fifth recordingpacket in leaving a space at the trailing end of the effective recordingfield of the fifth recording packet. Then the space is assigned for theother 3 bytes volume reserved data field or the dummy data field.

FIG. 24 shows an eleventh modification of the packet conversion systemaccording to the present invention. In this modification, the volume ofthe transmission packet is also set to 188 bytes in length, similar tothe MPEG transport packet. While volume of the recording packet is setto 90 bytes in length as in the above first through ninth embodiments.Then, the first byte on the head of the transmission packet is assigneda sync signal with a fixed pattern for use in the transmission.

In this modification, the entire 188 bytes data volume of transmissionsignal of the transmission packet including the head portion 1 bytevolume synch signal is recorded in the recording packet, similar to theseventh embodiment as shown in FIG. 20. Further, the reserved data fieldor dummy data field is assigned to a portion next to the trail end ofeach of the transmission packet signals. Then the reserved data field orthe dummy data field is used as an additional parity signal.

As shown in FIG. 23, the first 76 bytes data of the first transmissionpacket signal is recorded on the first recording packet. The next 76bytes data of the first transmission packet signal is recorded on thesecond recording packet. Then the remaining 36 bytes data of the firsttransmission packet signal is recorded on the leading end of theeffective recording field of the third recording packet.

Next, the first 38 bytes data of the second transmission packet signalis recorded on the trailing end of the effective recording field of thethird recording packet, but spaced from the last 36 bytes data of thefirst transmission packet signal by the 2 bytes volume reserved datafield or the dummy data field. The next 76 bytes data of the secondtransmission packet signal is recorded on the fourth recording packet.Then the remaining 74 bytes data of the second transmission packetsignal is recorded on the leading end of the effective recording fieldof the fifth recording packet leaving a space at the trailing end of theeffective recording field of the fifth recording packet. Then the spaceis assigned for the other 2 bytes volume reserved data field or thedummy data field.

As described above, the present invention can provide an extremelypreferable packet conversion apparatus and system, having the effectsuch that a propagation of errors can be suppressed and also such thatthe circuit scale can be reduced.

While there have been illustrated and described what are at presentconsidered to be preferred embodiments of the present invention, it willbe understood by those skilled in the art that various changes andmodifications may be made, and equivalents may be substituted forelements thereof without departing from the true scope of the presentinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teaching of the presentinvention without departing from the central scope thereof. Therefor, itis intended that the present invention not be limited to the particularembodiment disclosed as the best mode contemplated for carrying out thepresent invention, but that the present invention includes allembodiments falling within the scope of the appended claims.

The foregoing description and the drawings are regarded by the applicantas including a variety of individually inventive concepts, some of whichmay lie partially or wholly outside the scope of some or all of thefollowing claims. The fact that the applicant has chosen at the time offiling of the present application to restrict the claimed scope ofprotection in accordance with the following claims is not to be taken asa disclaimer or alternative inventive concepts that are included in thecontents of the application and could be defined by claims differing inscope from the following claims.

What is claimed is:
 1. A packet conversion apparatus comprising:meansfor detecting heads of transmission packet signals; means responsive tothe detecting means for packetizing the transmission packet signals bysequentially arranging them into one or more recording packets so that aprescribed number of transmission packet signals are placed at specificpositions within one or more recording packets; a source for supplyingreserved data; and means for inserting the reserved data into portionsof the recording packets where no transmission packet signals arepresent to maintain positional relationships of the transmission packetsignals packed in the recording packets.
 2. A packet conversionapparatus as claimed in claim 1, wherein the packetizing means and thereserved data inserting means each include a storage device capable ofrecording one or more recording packets with the reserved data insertedtherein according to a controlled write/read operation for theprescribed number of transmission packet signals and the reserved data.3. A packet conversion apparatus as claimed in claim 1 wherein theportions of the recording packets have a length less than or equal to adifference between a length of the one or more recording packets and aneffective length of the prescribed number of transmission packetsignals.
 4. The packet conversion apparatus as claimed in claim 1wherein ID data is recorded in the portions.
 5. The packet conversionapparatus as claimed in claim 1 wherein the heads of the transmissionpacket signals are not recorded when the packetizing means sequentiallyarranges them into one or more recording packets,
 6. The packetconversion apparatus as claimed in claim 1 wherein the packetizing meansallocates one transmission packet signal over two recording packets, 7.The packet conversion apparatus as claimed in claim 1 wherein thepacketizing means allocates two transmission packet signals over threerecording packets.
 8. The packet conversion apparatus as claimed inclaim 1 wherein the packetizing means allocates two transmission packetsignals over five recording packets.
 9. A packet conversion systemcomprising the steps of:detecting heads of transmission packet signals;packetizing in response to the detection of the heads of thetransmission packet signals by sequentially arranging them into one ormore recording packets so that a prescribed number of transmissionpacket signals are placed at specific positions within one or morerecording packets; supplying reserved data; and inserting the reserveddata into portions of the recording packets where no transmission packetsignals are present to maintain positional relationships of thetransmission packet signals packed in the recording packets.
 10. Apacket conversion system as claimed in claim 9, wherein the packetizingstep and the reserved data inserting step are each carried out using astorage device capable of recording one or more recording packets withthe reserved data inserted therein according to a controlled write/readoperation for the prescribed number of transmission packets and thereserved data.
 11. A packet conversion system as claimed in claim 9wherein the portions of the recording packets have a length less than orequal to a difference between a length of the one or more recordingpackets and an effective length of the prescribed number of transmissionpacket signals.
 12. The packet conversion system as claimed in claim 9wherein the inserting step includes the step of recording ID data in theportions.
 13. The packet conversion system as claimed in claim 9 whereinthe heads of the transmission packet signals are not recorded during thepacketizing Step.
 14. The packet conversion system as claimed in claim 9wherein the packetizing step includes the step of allocating onetransmission packet signal over two recording packets.
 15. The packetconversion system as claimed in claim 9 wherein the packetizing stepincludes the step of allocating two transmission packet signals overthree recording packets.
 16. The packet conversion system as claimed inclaim 9 wherein the packetizing step includes the step of allocating twotransmission packet signals over five recording packets.